Maybe a swap was made in the store at some time or another, could also have been a mistake direct from H&R or the supplier made a stock swap to fill an order! Could also have been a special order by some retailer like Dick's and it didn't get purchased, so it ended up at another retailer. Did the barrel serial number engraving match the frame serial number?
FWIW, not all monte carlo stocks are too high for iron sight use, there are several different comb heights in same style stocks, I've made several side by side comparisons. Conversely, not all straight stocks have the same drop, some folks here need to use straight stocks for scope use, Lik2hunt coming to mind, it's just a matter of ergonomics.
Tim